The prime goal of this core is to provide expert histopathology services, facilities, and resources for investigations involving cell and tissue microscopic analyses. Our Histopathology Core was established in 2004 with funding from the COBRE in Stem Cell Biology and Regenerative Medicine (8P20GM103465), with Dr. Volkhard Lindner as the Core Director. The success of this core has engaged all Center investigators, attracted many investigators from our Institutes COBRE in Vascular Biology and Maine Medical Center, and a number of regional clients. Current services provided include the fixation and processing of specimens for frozen, paraffin and plastic embedded sectioning. A comprehensive spectrum of histological stains and specialty stains are offered. Detection of specific proteins by immunohistochemistry (IHC) is a key service, and our staff expertly develops and optimizes antigen retrieval, analysis, and versatile detection methods. This core facility has also developed and characterized highly specific rabbit monoclonal antibodies for the detection of several antigens where quality antibodies do not exist. In transitioning to Phase III, we outline several innovative features. First, we recently have developed the capacity to prepare custom tissue microarrays, and this is being applied to genetically engineered mouse models, human specimens, and mice generated from the Knockout Mutant Mouse Project (KOMP) at The Jackson Laboratory. This core will collaborate with the Mouse Transgenic Core of our sister COBRE in Vascular Biology to generate unique tissue arrays from this mutant mouse resource. In addition, Histopathology will collaborate with our Molecular Phenotyping Core (Oxburgh) to facilitate quantitative analysis of immunostained antigens. The ability to quantify both histological and immunostained specimens will significantly sharpen cellular and pathological phenotypic analysis of disease models and human pathological specimens. Thus, for Phase-Ill, our Histopathology Core is well-positioned to provide, and expand, comprehensive expert analyses of a broad spectrum of cell and tissue specimens.